Bleaching of jute



FIFtiSU? States 7 Claims ABSTRACT OF THE DISCLOSURE The process of bleaching jute and inhibiting subsequent yellowing of the bleached jute under sunlight comprising treating the jute with an aqueous solution containing 8 to 12% by weight of the jute of potassium permanganate and 8 to 12% .by weight of the jute of a strong mineral acid and thereafter rinsing the jute in an aqueous solution of a reducing agent, and the resulting product.

The present invention relates to the bleaching of jute and more particularly to a process for bleaching jute which in addition to providing good whiteness of shade also inhibits subsequent yellowing of the bleached jute under the effects of light.

While jute is a highly useful fiber, and is used in enormous quantities in applications where color is of no con sequence, its use has heretofore been limited in fielda where color is a consideration, for example for use as draperies or other decorative fabrics. For such purposes jute has heretofore been bleached to produce'a desired light shade or preparatory to dyeing, to reasonably satisfactory whites by means of a hydrogen peroxide bleach. While the conventional hydrogen peroxide bleach provides an adequately light color initially, a difficulty has been that the whiteness'obtained is of a transient nature and the jute subsequently yellows as it ages, particularly rapidly under sunlight. Such defective light fastness of bleached jutes, dyed or undyed has been a decided detriment and has limited their use in the decorative field largely to uses of a novelty nature, a limited market.

An object of the invention is to provide a process for the bleaching of jute which will overcome the above mentioned disadvantages. h

Another object is to provide a process for Bleaching jute which will yield jute of light shade which is resistant to subsequent yellowing of the bleached jute under sunlight.

Another object is to provide a process for the treatment of bleached jute which will inhibit subsequent yellowing of the jute under light.

A further object is to provide a process for the bleaching and dyeing of jute wherein subsequent color change of the bleached and subsequently dyed jute is reduced, as contrasted with the products of bleaching and dyeing processes heretofore available.

A further object is to provide a bleached jute which is resistant to subsequent yellowing under exposure to light.

Further objects, features and advantages of the invention will become apparent from the following description.

In accordance with the invention, We have found that jute can be bleached to a good shade of whiteness with superior retention of shade and inhibition of subsequent yellowing of the bleached jute, both dyed and undyed, by treating the jute in an aqueous medium with potassium permanganate in the presence of a strong mineral acid, typically sulfuric acid, and subsequently clearing the jute of reduced permanganate by rinsing the jute in an aqu- WRQVQJM that MIN-HUL- 3,472,609 Patented Oct. 14, 1969 eous solution of a reducing agent, the amount of ,the potassium permanganate ranging between 8% and 12% by weight of the jute and the amount of the sulfuric acid being between 8% and 12% by weight of the jute. Somewhat better results can be obtained by applying the potassium permanganate and acid in a successionnof divided portions, the total amount however being: the same as that stated above, and following each application with a rinse inv a reducing agent. Improved results as to the degree of whiteness obtained can be produced by first bleaching the jute with a conventional hydrogen peroxide bleach and thereafter treating it as described with the potassium permanganate and acid. The invention is further described by the following specific examples of particular applications thereof, which are given by way of illustration and disclosure and not of limitations.

Example I A 900 pound roll of burlap fabric (300 lbs. dry Weight of fabric, 600 pounds water) was processed in open width on a standard open jig. The jig was prepared by adding to 50 gallons of water at 65 F. in the jig, 30 lbs. of potassium permanganate, (dissolved in the minimum amount of water) and 30 lbs. of sulfuric acid, 66": B. The fabric was then run, back and forth, for 20 minutes, when the active permanganate was exhausted. Thegbath was dropped and replaced with water at 190 F. containing 60 lbs. of sodium bisulfite (dissolved in the minimum amount of water) and the fabric run for 15 minutes. Upon drying, the fabric was found to be well bleached and when tested in -'a standard Fadeometer, according to AATC (2) Standard Test method l6A-l963, showed no appreciable shade change after 10 hours, only ai'slight shade change after 20 hours, and no substantial further change after hours. In contrast, the same oniginal fabric when bleached only by a conventional hydrogen peroxide bleach showed a substantial and objectionable shade change after 10 hours exposure. When dyed by conventional procedure, as used in the dyeing of cotton, with Vat Red 13, colori index No. 70,320, the fabric of this example when tested in the Fadeometer showed ,rio appreciable color chaiige after 10 hours, only a slight shade change after 20 hours and no substantial further change after 80 hours. In contrast, the same original fabric bleached only by a conventional hydrogen peroxide bleach and dyed in the same way with the same dyestuif showed a substantial and objectionable shade change after 10 hours.

Example II The procedure of Example I was repeated without change except to decrease the amounts of potassium per= manganate and of sulfuric acid to 24 lbs. each. The shade change after 20 hours, and after 80 hours, was greater in each case than in Example I but not as great as with the fabric bleached with hydrogen peroxide only.

Example III- The procedure of Example I was repeated without change except to increase the amounts of potassium permanganate and of sulfuric acid to 36 lbs. each. The color change after 20 hours, and after 80 hours, was somewhat less in each case than in Example I.

Example IV The procedure of Example I was repeated without change except to rinse the fabric in cold water following the permanganate treatment but before the sodium bi sulfite treatment, with slightly better results than in Example I.

3 Example V The procedure of Example I was repeated, substituting for the sodium bisulfite step a step comprising running the fabric once in each direction in a bath of water at"200 F. containing 15 lbs. of sodium sulfoxylate formaldehyde followed by addition of formic acid to the bath to bring the pH to 3.0-3.5 and running of the fabric for 20 minutes at 200 F. The results were better than in Example I in that the fabric showed a whiter shade.

I Example VI The procedure of Example I was repeated without change except to add the permanganate and sulfuric acid in four separate additions of 7.5 lbs. of permanganate and 7.5 lbs. of acid at each addition, and following each addition the fabric was treated, as in Example I, with 15 lbs. of sodium bisulfite. The results were slightly better than in Example I.

Example VII The procedure of Example I was repeated without change except to first bleach the jute with hydrogen per oxide by a conventional procedure before carrying out the other steps. The resulting fabric showed a whiter shade as compared with the product of the foregoing examples and equally good for better shade retention in the Fadeometer tests as compared with the fabric bleached with hydrogen peroxide only.

Example VIII A standard open jig was prepared with a bath containing 50 gallons of water at 200 F. containing pounds of olate soap and /2 pound of trisodium phosphate. A 900 pound roll of burlap fabric (300 pounds dry weight of fabric, 600 lbs. water) was scoured by running it back and forth in open width on the jig for 20 minutes. The bath. was dropped and replaced by a water bath at 150 F. and the burlap rinsed by passing it once in each direction through the bath, the bath dropped and replaced by cold water and the burlap again rinsed by passing it once in each direction through the bath. The burlap was then given a peroxide bleach by passing it once in each direction through a bath in the jig containing 3 pounds of sodium salt of ethylene diaminetetraacetic acid, 35 lbs. of trisodium phosphate, 30 lbs. of commercial grade sodium silicate and 2.5 lbs. of Exol- K--145 (bleaching assistant comprising potassium salt of fatty esters and solvents), the use of this or other as sistant being optional, When the burlap had been passed once in each direction through the bath, 20 lbs. of 35% hydrogen peroxide was added to the bath and the burlap passed once in each direction through the bath as the temperature was gradually raised to 120 F. The run was thereafter continued for 30 minutes as the temperature was raised to 160 F. and the burlap then run an additional 60 min. at 160 F. The bath was dropped and the burlap rinsed by passing it once in each direction through a bath of water at 160 F. and then once in each direction through a bath of cold water. The bath was dropped and replaced with a bath of water at room temperature and the burlap run at room temperature once in each direction as there was added to the bath at approximately equally spaced intervals 36' pounds of potassium per= manganate and 36 lbs. of sulfuric acid, 66 Baum, the bath temperature being maintained at 65 F. to 70 F., whereafter the fabric was run an additional 15 minutes at 65 -70 F. The bath was dropped and the fabric rinsed by passing it once in each direction through a water bath at 65 -70 F. The bath was replaced by a bath of water containing 15 lbs. of sodium sulfoxylate formaldehyde and the burlap run once in each direction at 65 --70 F. Oxalic acid was then added to the bath'in the amount required to bring the pH to between 3.0 and 3.5 (approx. 4.5 lbs.) and the fabric run for 20 minutes at 200 F.

The resulting fabric showed a whiter shade as compared with the products of Examples I through VI, in which no hydrogen peroxide bleach was employed, and had especially excellent resistance to artificial sunlight deterioration, showing even less shade change upon exposure in the Fadeometer than did the products of the preceding examples, and considerably less fading at 60 to standard Fadeometer hours than the same fabric bleached only with hydrogen peroxide showed in 10 hours. When dyed with Vat Red 13, color index No. 70,320 by standard procedure used in the dyeing of cotton, the resulting fabric showed excellent color shade and light fastness with acceptable shade retention after 80 standard Fadeometer hours exposure. In contrast the same original fabric after bleaching only by a conventional hydrogen peroxide bleach showed a substantial and objectionable shade change after only 10 hours exposure, both before and after dyeing.

As indicated in the examples, the bleached burlap of the invention, as compared with the conventionally bleached burlaps which show a significant yellowing after 5 or 10 standard Fadeometer hours, is highly resistant to yellow reversion and shows considerably less fading at 60 to 80 standard Fadeometer hours than burlap bleached with hydrogen peroxide alone would have shown in 10 hours. This difference is substantial and important because 10 standard Fadeometer hours represents only a small fraction of the desirable resistance to fading which should be possessed by a decorative fabric whereas a fabric which remains satisfactory after 60 to 80 hours on the Fadeometer is an acceptable fabric for decorative purposes, even including use as drapery material, which requires a high degree of light fastness. Such stabilizing elfect of the process of the invention makes possible the dyeing of the product in light to medium shades which show a color fastness more nearly like that expected from the same dyes on bleached cotton. Equivalent dyeings on hydrogen peroxide bleached jute show noticeable shade changes upon exposure to sunlight, regardless of dyestuff stability, within 10 to 20 hours of exposure to artificial sunlight. With the burlaps made possible by the invention the ultimate light fastness of a dyed burlap now depends on the light fastness of the dyestuff rather than upon the deteriorative change in shade of the jute itself as before.

In the process of the invention the use of more than 8% of potassium permanganate, based on the Weight of the jute, is critical as lesser amounts do not produce the degree of light fastness which is essential in decorative fabrics. Amounts above 12% confer little added benefit, if any.

Amounts of sodium bisulfite in the range 10% to 20% by weight of the jute are satisfactory and may be employed at room temperature, or, with more rapid results, at somewhat elevated temperatures up to about 88 C.

While it is not essential, we prefer that the jute be first scoured, as in Exampl VIII, as such scouring not only produces a better quality final product but dirt and other impurities removed in the scour would, if not removed, only tend to use up the chemical reagents.

While sulfuric acid is preferred, the other strong mineral acids, phosphoric, nitric and hydrochloric, can be used in equivalent amounts.

It is somewhat preferable to follow the potassium permanganate treatment with a rinse in clear water before clearing the reduced permanganate from the jute by the rinse in a reducing agent employed in the examples.

When particularly white shades of the bleached jute are desired we prefer to precede the permanganate-acid treatment by a hydrogen peroxide bleach. Such bleaches may be of the conventional types well known in the art. In such bleaching procedure, the hydrogen peroxide addition may be made in two steps, one-half at room temperature and the remaining half at F. Example VIII gives an instance of hydrogen peroxide bleach particularly adapted to effective use with the bleaching and light stabilization treatment of the invention.

As indicated in the examples, sodium sulfoxylate formaldehyde or equivalent is somewhat preferred as the clearing agent as the resulting products show whiter shades. Amounts in the range 3%-5% by weight on the fabric are satisfactory but not critical.

The bleaching and stabilization treatment of the inventon has been found to apply to jute of various grades,

v including the poorer grades known as common, the

intermediate grades known as AB, and th better grades known as Brites. The invention is applicable to jute in any form, e.g., fiber, yarn, or fabric, and to blends of jute with other fibers, serving to bleach and stabilize the jute component.

The products of the bleaching and stabilization treatment of the invention are well adapted to dyeing with any of the dyestuffs which are known for use with cotton and other cellulosic materials. This 'may be, for example, a direct, cotton, sulphur, naphthol, or vat dye which is used in dyeing cellulosic fibers such as cotton and rayon, herein for convenience referred to as cellulosic-type dyestuffs. The stabilized product is suitable for dyeing in 1 full or pastel shades.

We claim:

1. The process for bleaching jute and inhibiting subsequent yellowing of the bleached jute under sunlight which comprises treating the jute with an aqueous solution consisting essentially of 8% to 12% by weight of the jute of potassium permanganate and 8% to 12% by weight of the jute of sulphuric acid, and subsequently which comprises treating the jute with an aqueous solution consisting essentially of potassium permanganate and sulfuric acid and subsequently clearing the reduced permanganate from the jute by rinsing the jute in an aqueous solution of a reducing agent, and repeating said treating and rinsing steps in the order stated, the total amounts of each of the potassium permanganate and the sulfuric acid employed being 8% to 12% by weight of the jute.

5. The process for bleaching jute and inhibiting subsequent yellowing of the bleached jute under sunlight which comprises bleaching the jut with hydrogen peroxide, treating the so bleached jute with an aqueous solution consisting essentially of 8% to 12% by weight of the jute of potassium permanganate and 8% to 12% by weight of the jute of sulfuric acid, subsequently clearing the reduced permanganate from the jute by rinsing the jute in an aqueous solution of sodium sulfoxylate formal-= dehyde and oxalic acid at a pH of 3.0 to 3.5.

6. A bleached jute, being the product of the process of claim 1. v

7. A bleached jute, being the product of the process of claim 3.

- References Cited UNITED STATES PATENTS 534,450 2/1895 Clapham et al. 8111 1,032,151 9/1912 Maupai 88-411 2,018,276 10/1955 McKee et a1. 8107 2,172,233 19/1959 Wilson 8-107 XR 2,173,474 9/1959 Evoy 8111 3,384,444 5/1968 Simpson et al. c 8111 OTHER REFERENCES Rose et al.: Condensed Chemical Dict., 1961, 6th ed., p. 1042 relied on.

MAYER WEINBLATT, Primary Examiner U.S. Cl. X.R.-. 8-107; 252 

